cpp11-migrate: Fix parsing of '.' for header include/excludes

sys::fs::make_absolute was turning '.' into '<path>/.' which broke prefix
comparison logic. Stripping these extra chars fixes the problem.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@184322 91177308-0d34-0410-b5e6-96231b3b80d8
cpp11-migrate: Fixing doxygen warning



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@184326 91177308-0d34-0410-b5e6-96231b3b80d8